Knurling device



Oct. 6, 1953 c. F. JONES 2,654,273

KNURLING DEVICE Filed April 12, 1949 4 Sheets-Sheet 1 Oct. 6, 1953 c. F. JONES 2,654,273

KNURLING DEVICE Filed April 12, 1949 4 Sheets-Sheet 2 gergyzuj Jaw Oct. 6, 1953 c, JONES 2,654,273

KNURLING DEVICE Filed April 12, 1949 4 Sheets-Sheet 3 IN V EN TOR.

gerr zgwifanea Patented Oct. 6, 1 953 KNURLING DEVICE Cernyw F. Jones, Economy, Ind., assignor to Perfect Circle Corporation, Hagerstown, Ind., a corporation of Indiana Application April 12, 1949, Serial No. 87,094

12 Claims.

This invention relates generally to knurling devices for knurling the peripheral surface of a cylindrical object and more particularly to devices for knurling predetermined areas on the peripheral surface of a hollow cylindrical article such as a piston for an internal combustion engine.

With continued operation of an interna1 combustion engine, the pistons and cylinders tend to wear or become distorted with the result that the normal fit of the pistons within the cylinders is lost. This condition is often characterized by piston slap and other evidence of excessive looseness. The lack of a proper fit between the piston and the cylinder is objectionable since it impairs engine efliciency and has an adverse effect on the economy of operation.

Various means for correcting this condition have been employed, one method involving the expansion of the outer wall or skirt portion of the piston sufficiently to reestablish the normal fit between piston and cylinder. Such expansion may be accomplished, for example, by knurling the outer surface of the piston to form roughened areas on the thrust faces thereof having an interrupted surface comprising projecting por-' tions with intervening depressions. During knurling the metal is extruded or swaged to a sufi'icient extent so that the projections formed on the piston surface extend outwardly to the.

desired increased size whereby the proper fit between the piston and the cylinder is realized.

A machine or tool for knurling the outer surface of a hollow piston should preferably be provided with an anvil member or other supporting means adapted to engage and support the piston internally while a knurling element engages the exterior of the piston under pressure. However, the interior surface of the skirt portion of a piston is usually quite uneven in the area between the wrist pin bosses, because of various pro tuberances and surface irregularities such as reinforcing ribs, partial machining of the interior surface, and general surface roughness characteristic of cast articles. Thus, the problem is presented of providing a knurling device which will readily accommodate the variations in piston wall thickness while at the same time avoiding any substantial change in knurling pressure against the outer surface of the piston.

Accordingly, a primary object of my invention is to provide a device for knurling the exterior surfaces of pistons which readily accommodates variations in piston wall thickness while maint ini g a sub t ntia y c ns a t knurling pressure.

Another object of my invention is to provide a device for knurling the exterior surfaces of pistons in which a supporting member engages the interior of the piston, a knurling member engages the exterior of the piston, and the spacing between said members is permitted to vary automatically to accommodate protuberances and other irregularities on the interior surface of the piston.

An additional object of the invention is to provide a hand operated device for knurling the exterior surfaces of pistons which is of simple rugged construction and is relatively portable in the sense that it requires no permanent mounting and may, for example, be held in a vise or be detachably secured to a bench or other support.

Other objects and advantages of the invention will become apparent from the subsequent detailed description of the invention and the accompanying drawings, in which:

Fig. 1 is a fragmentary side elevational view of a knurling device comprising one specific embodiment of my invention;

Fig. 2 is a top plan view of the device as shown inFig. 1;

Fig. 3 is a vertical sectional view taken along the line 3--3 of Fig. 1;

Fig. 4 is a top plan view of a knurling device comprising a different embodiment of the invention;

Fig. 5 is a rear elevation view of the device when positioned as shown in Fig. 4;

Fig. 6 is a fragmentary end view of the device when viewed from the right in Fig. 4;

Fig. 7 is a fragmentary end view of the device when viewed from the left in Fig. 4;

Fig. 8 is a vertical sectional view of still another form of the invention taken along the line 8-8 of Fig. 9;

Fig. 9 is a top plan view of the device as shown in Fig. 8;

Fig. 10 is an end view, with portions thereof in section, as viewed from the left in Figs. 8 and 9; and

Fig. 11 is a fragmentary end view, with portions thereof in section, as viewed from the right in Figs. 8 and 9.

As heretofore mentioned, the knurling device comprising the present invention is provided with a pair of cooperating anvil and knurling elements, the anvil element being arranged to support the piston internally while the knurling element bears against the outer surface of the piston. The knurling element is preferably in the form of a small roller which is applied to the outer surface of the piston in rolling relation therewith so that the resultant area knurled in one application of the tool comprises a band having a width equal to the width of the roller. Usually the roller is relatively narrow and transverses the piston circumferentially so that a plurality of such knurled bands are required to cover a desired area longitudinally of the piston. The knurled bands may, of course, be disposed in continuous abutting relation to one another or they may be slightly spaced from each other longitudinally of the piston.

With a piston for an internal combustion engine, it is necessary to knurl only the thrust faces of the piston skirt, i. e. those portions which are subjected to lateral thrust against the cylinder wall due to the position of the connecting rod. Thus, the iznurling operation may be restricted to the portions of the piston skirt lying intermediate the wrist-pin holes on opposite sides of the piston. The knurled area preferably starts immediately below the bottom ring groove in the piston and may extend axially or longitudinally for the full length of the piston skirt. If desired, the knurled band at the extreme outer end of the skirt may be spaced difierently from the remaining bands in order to position the outermost band as close as possible to the edge of the piston.

In addition to effecting expansion of the piston metal by extrusion thereof, in the manner hereinbefore described, whereby to reestablish a proper fit between the piston and the cylinder, the knurled surface obtained by my invention also offers other important advantages. For example, it has been found that better performance is obtained in a reciprocating piston and cylinder,

7 or other like construction, if one of the two surfaces is of an interrupted nature comprising projecting portions with intervening depressions, such as may be provided by knurling. A surface of this character has been found to run cooler than an absolutely smooth surface for pistons as well as other cylindrical objects adapted to reciprocate within a bore. Another advantage inherent in knurling the surfaces of pistons and like articles is found in the improved wearing qualities of the knurled surface resulting from the hardening effects of cold working the metal.

It will be apparent, therefore, that, in addition to the obvious utility of knurling old or worn pistons in order to expand the same, knurling may also'be resorted to in the case of new pistons or original assemblies of pistons within their cylinders in order. to attain the other advantages mentioned above. While the knurling devices comprising the present invention are designed primarily for knurling pistons,

the invention is not limited in this manner but embraces the knurling of the peripheral surfaces of hollow cylndrical articles generally.

The term knurling as used throughout the specification and the claims is not limited to the ordinary form of knurling involving grooves arranged in a criss-cross pattern, but rather is used in a broad sense to include any surface formation involving alternate depressed and raised portions regardless of whether one or the other or both of said portions are continuous throughout the area having such formation. Thus, the term includes not only the criss-cross pattern but also a pattern formed by parallel grooves or by isolated indentations resulting in connected raised portions.

As hereinbefore mentioned, the primary object of my invention is to provide a knurling device for pistons, which is designed to accommodate varying piston wall thicknesses due to internal protuberances or surface irregularities while at the same time avoiding substantial changes in knurling pressure and eliminating the need for manually adjusting or regulating the device during a knurling operation. I accomplish this end broadly by providing a pair of cooperating anvil and knurling members which are operatively connected for pivotal movement toward and away from each other, in combination with a spring means for yieldingly urging the anvil and knurling members toward each other. The yieldable urging of the two members toward each other permits a variation in spacing between the members upon contact of the anvil member with protuberances on the interior surface of the piston skirt while the knurling member bears with substantially constant'pressure against the exterior surface of the skirt.

The detailed structure for obtaining this yielda-ble relationship of the parts of the device may comprise any one of numerous different forms, but for purposes of explaining my invention three specific and preferred embodiments of the invention are illustrated in the drawings.

Form shown in Figs. 1-3

In the form of the invention illustrated in Figs. -3, there is provided a rigid elongated supporting structure or body member, indicated generally at 2|, having a relatively thin flat end portion 22 adapted to be received between the clamping jaws of a vise for supporting the device. A bracket or arm 23 extends longitudinally at the opposite end of the body member 2| for supporting a knurling member in the form of a roller 2d. The roller 24 is mounted for rotation adjacent the outermost end of the arm 23 by means of a pair of bearing sleeves 26 keyed to the roller 24, the bearing sleeves 2B and the knurling roller 24 being clamped together and secured to the end of a drive shaft 2'! by means of a stud 28 extending longitudinally through the sleeves and the roller and threaded into the shaft 21. A nut 29 is mounted at the outer end of the stud 28 for securing the sleeves 2'6 and roller 24 in clamped relation. The drive shaft 21 extends longitudinally of the base member 2! and is journaled at its opposite end in a bearing bracket 3| projecting upwardly from the vise clamping portions 22. A hand crank 32 extends through an aperture adjacent the end of the drive shaft 21 for manually driving the knurling roller 24 and is adjustably secured thereto by means of a set screw 33.

A lever in the form of a bell crank, indicated generally at 34 and comprising an upright leg 35 and a horizontal leg 3?, is pivotally supported of spaced rearwardly projecting ears G0 on the body member 2|. The pin 38 i retained in the ears to by means of a pair of end washers 39 secured by a pair of screws 5! to the pin 33 and bearing against the ears 4!] (Fig. 2). An elongated anvil-supporting arm d2 extends laterally from the upper end of the upright leg 36 in a direction generally parallel to the knurl-supporting arm 23 and the drive shaft 2?, the arm 42 being fastened to the upper end of the leg 36 by means of a pair of screws 43. The outermost end of the arm 42 is provided with a pair of spaced projections between which is mounted for free rolling movement an anvil member in the form of a hard smooth-surfaced roller 44 having approximately the same diameter and width as the knurling roller 24. The anvil roller 44 rotates about a shaft or pin 45 and is urged outwardly by means of a coil spring 46 encircling the pin 45 whereby the anvil roller 44 is maintained in radial alignment with respect to the knurling roller 24. 7

It will be seen that by rocking movement of the bell crank 34 about the fulcrum pin 38, the arm 42 and the anvil roller 44 carried thereon may be moved away from and toward the knurling roller 24. During a, knurling operation, the skirt portion 41 of a piston, indicated by broken lines in Figs. 2 and 3, is clamped between the two rollers, the anvil roller 44 being disposed against the interior surface of the piston skirt and the knurling roller 24 bearing against the outer periphery of the piston skirt with the axes of the rollers being parallel to the axis of the piston.

The horizontal leg 31 of the bell crank 34 is bifurcated at its outer or forward end, as at 48, and is provided with a rotatable pin or shaft 49 extending transversely therethrough. An upright spring loading device, indicated generally at 50, coacts with the bell crank 34 for applying adjustable yielding pressure against the horizontal leg 31 in order to normally urge the anvil roller 44 toward the knurling roller 24. To this end, an elongated screw 5| having terminal threaded portions extends longitudinally between the branches 48 of the bifurcated leg 31 and through a transverse aperture in the shaft 49. The lower end of the screw 5| is received within an enlarged concentric bore 52 in a boss 54 formed in the lower portion of the base member 2| and is threaded in a swivel 53 which is in the form of a shaft rotatably supported in the boss 54 transversely of the bore 52. Encircling the screw 5| is a helical spring 55 adapted to apply yielding pressure against the shaft 49 through a thrust collar 56 comprising a plurality of loosely mounted thrust washers. A spring load adjusting nut 51 is threaded on the screw 5| and bears against the upper end of the spring 55 through a similar thrust collar 58. Disposed below the shaft 49 i a lowermost thrust collar comprising a washer 59 rigidly secured to the screw 5| and a washer 6| resting loosely thereon for engaging the shaft 49 and urging the latter upwardly during movement of the anvil roller 44 to released position, as hereinafter described in detail. A hand crank 62 is fastened to the upper end of the screw 5| for rotating the same.

By adjusting the nut 51, the tension of the spring 55 can be regulated to control the downward pressure exerted on the leg 31 of the bell crank 34 and thereby regulating the knurling pressure, i. e. the pressure under which the piston skirt 4'! is pressed against the knurling roller 24 by means of the internal anvil roller 44. A jam nut 63 is carried on the screw 5| above the adiusting nut 51 for locking the latter in place after the spring tension has been adjusted to any desired extent.

The operation of the spring loading device 59 is as follows: In the position shown in Fig. 3, the screw 5| has been screwed downwardly through its threaded connection with the swivel 53 a sufiicient distance so that a slight clearance, indicated at 64, is established between the thrust washer 6| and the shaft 49. Thus, the full pres sure of the spring 55 is brought to bear down- -wardly on the shaft 49 thereby urging thebell crank 34 in a counterclockwise direction, as viewed in Fig. 3, and causing the anvil roller 44 'to be pressed toward the knurling roller 24 with the piston skirt 41 being clamped therebetween. As described above, the knurling pressure may be controlled by adjusting the nut 51 to regulate the tension of the spring 55.

By means of the hand crank 62, the screw 5| may be screwed outwardly from the swivel 53 until the thrust washer 6| abuts the bottom portion of the shaft 49 thereby rendering the spring load ineffective as the clearance 64 is taken up. At this point, continued backing away of the screw 5| causes the leg 31 to be rocked upwardly and the anvil roller 44 to be moved away from the interior surface of the piston skirt 41 to released position as the bell crank 34 rotates in a clockwise direction about the fulcrum pin 38, as viewed in Fig. 3. With the rollers 24 and 44 in radially spaced position, the piston skirt may be withdrawn or inserted between the rollers to the desired extent. As the leg 31 swings upwardly in an arcuate path during movement of the anvil roller 44 to released position, the screw 5| pivots slightly to the right, as viewed in Fig. 3, in a transverse plane relative to the elongated base 2|. To accommodate this pivotal movement of the screw 5|, the shaft 49 and the swivel '53 rotate freely in their respective supporting structures, the bifurcated end 48 of the leg 31 and the enlarged bore 52 providing sufiicient clearance to permit the screw 5| to assume the necessary angular position.

During the backing away of the screw 5|, the tension setting of the spring 55 is not materially disturbed since the spring tension is determined by the relative position of the adjusting nut 51 on the screw 5|. Upward movement of the screw 5| from the position shown in Fig. 3 until the clearance 64 is taken up will result in a very slight decrease in the spring tension setting equivalent to the extent of the clearance 64, but this change is of no practical consequence. Thus, it will be seen that the anvil roller 44 can be backed away from the piston skirt 41 without unloading the spring 55 or otherwise changing the spring tension setting.

To return the device to knurling position, the hand crank 62 is operated in reverse fashion whereby the screw 5| is screwed downwardly through the swivel 53 and the tension of the spring 55 acting on the shaft 49 pivots the bell crank 34 to swing the anvil roller 44 into contact with the inner surface of the piston skirt 41 with 'suflicient pressure to sink the ridges on the knurling roller into the outer surface of the piston skirt. Further movement of the bell crank 34 and its leg 31 is prevented, and downward movement of the screw 5| is continued until the slight clearance 64 is reestablished between the shaft 49 and the thrust washer 6|. Thus, the spring is returned substantially to its original tension and the full spring load is again imposed on the shaft 49. Once the clearance 64 is obtained, further operation of the hand crank 62 is unnecessary since the establishment of the slightest clearance at this point permits the full spring tension, as determined by the setting of the nut 51, to be applied against the shaft 49.

In knurling pistons with the device shown in Figs. 1 to 3, a piston skirt is first inserted between the rollers While the arm 42 is in released position. Upon adjustment of the nut 51 to obtain the desired spring pressure and upon rotation or the crank 62 to return the arm 42 to operating position, the desired. knurling operation may be carried out by rotating the hand crank 32 which drives the knurling roller 26. During knurling, the piston is stabilized in a horizontal plane by the clamping action of the rollers 24 and t4 and, in the present form of the invention, is stabilized in a vertical plane by the hand of the operator. Rotation of the crank 32 results in relative rolling. movement between the knurling roller 25 and the piston circumferentially of the latter. Because the piston skirt er is clamped between the rollers 25 and d4, rotation of the knurling roller 2d also causes simultaneous rotation of the piston about its axis whereby to form an arcuate knurled band on the outer periphery of the piston skirt as herein iefore described.

During the course of a knurling operation, if the anvil roller 44 encounters internal protuberances or other surface irregularities on the interior of the piston skirt 41, it will be seen that the yielding application of the roller 2 against the inner surface of the piston skirt permits the roller to be forced away from the protuberance, the bell crank 35 rocking in a clockwise dire"- tic-n about the fulcrum pin 38 and the horizontal leg 3'. being forced upwardly against the action of the spring 55. The slight compression of the spring 55 resulting from such rocking movement will have no significant effect on the pressure under which the piston skirt is clamped between the rollers 2:3 and id. Thus, my device provides for substantially constant knurling pressure, as predetermined by the setting of the adjusting nut 5", even when the radial spacing between the rollers M and ti varies as the anvil roller c t passes over surface irregularities on the interior of the piston skirt.

As hereinbefore mentioned, the diameters and widths of the knurling roller 2 and the anvil roller 44 are preferabl substantially the same. Such a relationship insures that the anvil roller will have an area of engagement with the interior of the piston skirt which lies substantially within the area of the engagement of the rolling knurl with the exterior of the skirt, thereby avoiding any possibility of distorting the shape of the piston as a result of the pressure between the knurling and anvil rollers, except for the increase in diameter due to the swaging action of the knurling roller.

Form shown in Figs. 4-7

This embodiment of my invention is generally similar to the form described above and differs principally in that the anvil-supporting arm pivots directly on the base structure thereby eliminating the bell crank arrangement shown in Figs. 1-3. In addition, a modified form of the spring loading device is utilized.

The device comprises a rigid elongated body member, indicated generally at H, with a depending vise-clamping portion 12 at one end similar to the arrangement shown in Figs. 1-3. An elongated arm 73 extends longitudinally at the opposite end of the body member H for supporting a knurling roller is which is operatively connected to the end of a drive shaft 15 by means of a bearing sleeve and stud assembly, as in Figs. 1-3. The drive shaft 15 is journaled at its opposite end in the body member ".H and a hand crank it is provided for manually driving the knurling roller M. An elongated anvil-supporting arm ll carrying an anvil roller 58 at its outermost end is rockably mounted on the body member H. The opposite end of the arm 17 is enlarged, as at 19, and is mounted in a slot 8!) in the body member H. The arm l'l' is pivotally supported at its enlarged end it on a knife edge member 8! rigidly attached to the body member H by means of a pair of screws 82 and extending transversely of the slot 83. The knife edge of the member 8! is received within a notch 83 on the inner face of the arm ":1, the sides of the notch intersecting at an angle greater than the angle of the member 8i (Fig. 4) whereby to permit rocking movement of the arm 7 on the knife edge 8| as a fulcrum.

The spring loading device, indicated generally at 84, is similar to that shown in Figs. 1-3, but in this instance engages the arm 11 intermediate the anvil roller 18 and the knife edge member 8! and coacts with the base member H for yieldingly urging the anvil roller 78 toward the knurling roller M. The spring loading device 84 comprises an externally threaded stem 85 having a flanged end 86 with a washer 8'5 loosely supported thereon. The flanged end 86 is received within an enlarged recess 88 in the outer face of the arm 11, the recess 88 being somewhat larger than the flanged end 86. The outer end of the stem 85 is provided with a handle 39 for eiiecting rotation of the stem 85. A helical spring encircles the stem 85, bearing at one end against a thrust collar 9| comprising a loosely mounted washer which overlies the recess 88 and engages the outer face or" the arm H. The spring as is retained at its other end by a tension adjusting nut 92 and a thrust collar 83 comprising a plurality of thrust washers. A locknut or jam nut 94 is also provided adjacent the nut 92 for locking the latter in place in order to maintain any desired tension setting of the spring 88. A stud 96 is threaded into an. axial bore 91 at the inner end of the stem 85 and extends at its opposite end through an aperture 98 in the arm H, the aperture 98 being somewhat larger than the stud 86. The innermost end of the stud 96 is rigidly secured, as by threads, to a swivel 99 in the form of a shaft or pin journaled in the body member ll.

As viewed in Fig. 4, the stem 85 is screwed inwardly relative to the stud 96 a sufiicient amount so that a slight clearance, indicated at (Bl, exists between the washer 31 and the thrust collar 9!. In this position the full load of the spring 96 is imposed on the arm l1 thereby yieldingly urging the anvil roller 78 toward the knurling roller 1'4. In Figs. 4 and 7, a piston is shown in broken lines at "32 with the skirt portion being clamped between the rollers 1 1 and 28.

To release the knurling pressure, the stem 85 is screwed outwardly by the handle 89. As the clearance I0! is taken up, the washer 8? on the flange portion 86 engages the thrust collar 9!, and upon continued backing away of the stem 85 the thrust collar Si is moved out of engagement with the outer face of the arm H to provide a space or clearance therebetween. With the thrust collar 91 spaced from the arm H, the spring load is removed, thereby freeing the arm TI and permitting it to be pivoted manually about the knife edge 8| in order to move the anvil roller 78 outwardly away from the knurling roller M. As the arm ii is swung outwardly to released position, the stem 85 and its axially aligned stud 96 pivot slightly to the right, as viewed in Fig. 4, as the swivel 99 rotates to accommodate the angular outwardly pivoted position of the arm 11, the clearance between the flange 86 and the recess 88 and the clearance between the stud 96 and the aperture 98 permitting such pivotal movement.

As in the device 50. of Figs. 1-3, it will be seen that the spring load of the device 84 can be released from the arm TI without changing the setting of the tension adjusting means and without otherwise materially altering the spring pressure. The device 84 differs from the device 50 in Figs. 1-3 in that in the present form rotation of the handle 89 merely frees the arm 11 which may then be moved by hand to released position. In the device 50, and also in the form of the invention illustrated in Figs. 8-11 and hereinafter described in detail, releasing movement of the spring loading device also mechanically moves the anvil arm and the anvil roller to released position.

To return the device 84 to knurling position, the stem 85 is screwed inwardly until the thrust collar engages the outer face of the arm 11 and, when the anvil roller 18 contacts the piston skirt I 92, the stem 85 is screwed inwardly a slight distance farther until the clearance IIII is reestablished and the full spring load is thereby brought to bear on the arm 11 to sink the ridges on the knurling roller into the metal of the piston skirt.

During use of the knurling device, a piston skirt is first inserted between the rollers 14 and 18 while the anvil arm 11 is in released position. The device 84 is then manipulated to return the arm I1 and roller 18 to knurling position under a predetermined spring pressure as regulated by the adjusting nut 92. With the piston stabilized by the hand of the operator, as in the previously described form of the invention, the knurling roller 74 is then driven by the hand crank I6. As the anvil roller 18 encounters protruding conformations on the inner surface of the piston skirt, the roller I8 is forced away from the roller l4 without substantially changing the knurling pressure.

Form shown in Figs. 8-11 This modification of my invention differs from the two forms previously described in that the base or supporting structure is designed to be secured to a work-bench or other fiat horizontal surface, whereas the devices illustrated in Figs. 1-7 are provided with projecting vise-clamping portions adapted to be rigidly held between the jaws of a vise. The present modification also differs from the previously described forms by the provision of a work supporting structure integral with the device for supporting and stabilizing the alignment of a piston during a knurling operation.

The device comprises a base structure I II provided at its ends with a pair of apertured lugs H2 for screwing or bolting the device to a bench surface. At one end of the base I I I is a V-shaped trough comprising a pair of elongated side walls H3 extending upwardly in spaced parallel relation from the base III and terminating in outwardly sloping inclined portions H4 adapted to support the outer circumference of a piston as indicated in broken lines at H3 (Figs. 8 and A cylindrical socket portion II'I depends from the side walls H3 centrally of the trough structure and carries a knurl support in the form of a spring-pressed plunger H8 slidable within the socket I I! and having a forked upper end I20. A knurling roller H9 is journaled in the upper end I20 by means of a pair of bearing sleeves I2I keyed to the roller H9 and clamped. together vwith a stud I22 in the same manneras in the 10 forms of the invention illustrated in Figs. 1-7. The plunger H8 is pressed upwardly by means of a spring I23 bearing against the lower end of the plunger and retained by a plate I24 detachably fastened by a screw I26 (Fig. 10) to the endof the socket portion III. A manually operable locking screw I2Iprojects from the front of the device through the wall of the socket H! to engage a slanted recess I28 (Fig. 10) in the plunger I I8 for adjusting and locking the knurling roller H9 in any desired vertical position, as hereinafter described in detail.

The knurling roller H9 is driven by a hand crank I29 secured to a drive shaft I3I which is journaled in an upstanding bracket portion I32 at one end of the base III. The drive shaft I3I- is operably connected to the roller H9 by a connecting shaft I33 extending therebetween and having universal connections, indicated at I34 and I36 (Fig. 8),, at its ends for pivotally securing the same to the stud I22 and the end of the drive shaft I3I, respectively. By means of the universal connections I34 and I36, the knurling roller H9 may be driven at any elevation of the roller H9 relative to the shaft I3I and the hand crank I29. To prevent endwise movement of the shaft I3I and thereby insure proper functioning of the universal connections I34 and I36, a retaining screw I31 extends downwardly through the bracket portion I32 and engages a circumferential groove I38 in the shaft I3I.

To provide an anvil support, a lever I39 is pivotally supported at one end by a shaft or pin I49 journaled at the rear of the base III. Extending perpendicularly from the forward end of the lever I39 and secured thereto by a pair of screws MI is an elongated anvil-supporting arm I42 carrying an anvil roller I43 at its opposite end in radial alignment above the knurling roller II9. A spring loading device, indicated generally at I44, coacts with the base III and the lever I39 intermediate the ends of the latter for yieldingly urging the anvil arm I42 and the anvil roller I43 toward the knurling roller H9.

The spring loading device I44 is substantially the same as the device 50 illustrated in Figs. 1-3 and will, therefore, be described only brieny. A terminally threaded screw I46 extends downwardly through an enlarged aperture I41 (Fig. 11) in the lever I39 and through a shaft or pin I48 rotatably mounted in the lever I39. The lower end of the screw I46 is received within an enlarged vertical bore I49 in the base structure III and is threaded in a swivel in the form of a shaft or pin ISI journaled in the base III. A helical spring I52 is carried on the screw I46 between a pair of thrust collars I53 and I34 with a tension adjusting nut I56 and a jam nut Ie'l being provided to regulate the spring tension. A thrust collar I58 is rigidly secured on the screw I46 below the shaft I43 for engaging the latter to lift the lever I39 upon backing away of the screw I46. A handle [59 is amxeo to the upper end of the screw I46 for rotating the latter.

It will be apparent that the spring loading device I44 operates in a manner similar to the previously described device 50. As seen in Fig. 11, the screw I46 is screwed sufficiently into the swivel I5I to establish clearance, as at Io'l, between the shaft I48 and the thrust collar I58 thereby bringing the full spring load to bear on the lever I39. To release the anvil roller I43, the screw I46 is backed away by means of the handle I59, the clearance I6I is taken up, and the lever l39 and its attached anvil arm I42 are lifted away have the knurling roller i9. seen reieasaifie aperture l4} and the enlarged b'or'e M9 provide suffieierit clearance to permit the screw use to'pivdt uses rotation of the shaft Hi8 and the swivel- 15! whereby to cooperate with the ai'iiate swinging movement of the lever (39 LAS bst seen in Fig. 10, the piston HE is slippaired circumferentiall'y during a knurling OPf eraser;- by the inclined sides HE of the V-shaped trough; By adjusting the locking screw I21; the eitent' to the knurling roller llfiproje'cts upwardly between the inclined sides H4 can be 'CdIitiOlldto accommodate var ing piston diameters; In setting the krlu-i'l at the desired eleva= tion, l1 prefer to have the roller H9 extend upwardly between the inclined side's H4 a sufiieieht distance so that when the outer periphery oi the piston is held ihcoilt'ECt-With the kmirling roller 9 by the clamping action bf fih'innei anvil roller 143 the piston will be spaced from the inclinedsides M4 by a distance 'substantially equivalent to thede'gree of expansion or increased diameter which it is desired to impart tethe pie-'- ton skirt at that point; This maybe readily ac cOhLpI i'Sh'ed, for exam-pi ty 'l a y il l'g apiece or r shim stock of the requiredthickness across the v -shaped trough to oneside ofthe rollers 4 l9 and M3 and then holding the piston tightly in place by. hand while setting the-knurl. The shim stock may then be removed and the knuriing' operation carried out until the clearance between the piston and the inclined sides l-l4is-taken up as a result ofrthe expansion or the metal surface by the extrusion or swagi-ng action of-theknurlm'groller.

To avoid undesired distortionotthepisten, the knurl may be set so that the piston clears the trough initially by an -amount, e. g. -.003-inch, greater than the increased size which it is desired. to impart byknurling'v 'rnen'by inserting a..003:inchieeler gaugefror'n time to time between the piston and the-trough, it is possible to determine readi-ly when the piston been knurled to the'desired extent without any danger-of the anvil m'ex'nb erfibeing pressed against the interior of rthelspistonewhile rthesexteriornof thew-piston is supported by the trough.

AS jngthQjDITBVl-OUSlYQdESCIibBCLfOIHlS of thein vention the,,-yielding application. of the anvil roller 3 togthelinteriorcf:theipiston'skirtunder the pressure of thespr-ingiloadingsdevice i 44 permits the, anviliiroller .zto pass -over internal pro- ;tuberances,withoutvany substantial change in the lmurling pressure. Moreover, the anvil .lroller may be moved ;to released positionsfor-inserting or withdrawing a piston 'withoutunloading or otherwise disturbing the tension; setting, otthe device Although, the; invention hasrbeen described in detail with-reference to certain preferred structural embodiments, it will be understood that various modifications and equivalent structures may be. resorted to without departing from the scope of-the' invention as definedin the appended claims. 5

-I claim: 0 g

t. A linurlinr'gjdevice "comprising a supportin strut tur'ehavihg'abase member'and as'up'p'o'rting member pivotally mounted bn sa'id base "member, afjkn'urling element in the "form of'afrolle'r journalled in one of said members-an anvil eleiiien'tcarried'on the other of said members in -substantial alignmentwith said knurling'element whereby said elements are supported "in pivotal relation for -movement toward and away from movement between the knurling element and an article to be knurled, an elongated operating member, cooperating means on said base and op erating members for 'moving said operating member lengthwise, an abutment on said supporting member and a fixed stop on said operating member for engaging one side of said abutment for moving said elements apart on lengthwise movementof said operating member, and a spring on said; operating member engaging the opposite side of said abutment for urging said elements together when said operating member has been moved to spacesaid fixed stop from said abutment.

2'. The device of claim 1 further characterized in that said supporting structure comprises an elongated base member having a longitudinal slot at one end thereof, an elongated supporting member mounted: in said slot, and a knife edge at said one end" of said base extending transversely of said slot and having one end of said supporting member pivoted thereon; and said knurling and anvil elements are disposed at the opposite ends of said base and supporting members.

3'. The device of claim 1 further characterized in that said base member is adapted to be supported on a horizontal surface and is provided with a V-shaped trough for receiving and supporting the article to be knurled; and said linurling element is journalled in an upright knurl support, said knurl support being slidably mounted in said base member and extending upwardly between the inclined sides of said trough and having adjusting means cooperating therewith for positioning said knurling element relative to said trough.

'4. The deviceof claim 1 further characterized in that said base member is adapted to be supported on a horizontal surface and is provided with a work -support atone end thereof for receiving and holding the article to be knurled the knurling rolleris journalledin said base member adjacent said work support; said supporting member comprises a lever extending transversely of saidbase member at the opposite end thereof and pivotally secured at one end to said base member on an axis parallel to the axis of the k-nu-rling roller, and an elongated anvil arm secured; to the free end of said lever and extending longitudinally of said-base member; said anvil element is in the form of an anvil roller journalled at the outer end-of said anvil arm; and saidspringmeans coacts -between saidbase member and said lever with the anvil roller "being maintained on an axis parallel to the knuriing roller axis by the position of thepivotal axisof said lever.

-5j. -Dhe device of -claim 1 further characterized in that said base memberis adapted to be supiported on a horizontal surface and is provided with a V-shaped work-supporting trough; the linurling roller is journal-lied in the upper end \of an upright lanurl support which is slidably mounted for vertical movement relative to said 'base member and extends upwardly into said trough and-is provided with adjustable means coop eraiang therewith for p osi-tioningthaknurling roller at anvdesired elevation relative; to said trough; and said-means ior efiecting lrelative rolldn'g movement comprises a, manually operable drive shaitiournaHed insajidibase member and provided with universal connections with said linurling roller. ewliereby to driveflthe latter 'at anyidesired elevationathereof;

r 5 6. h lnurling flevice comprising asu poi img structure having a base member and'a supp ing member pivotally mounted on said base member, a knurling element in the form of a roller journalled in one of said members, an anvil element carried on the other of said members in substantial alignment with said knurling element whereby said elements are supported in pivotal relation for movement toward and away from each other, means for eiiecting relative rolling movement between the knurling element and an article to be knurled, and releasable spring means for yieldingly urging one of said elements toward-the other of said elements during said rolling movement whereby to clamp the article in knurling position therebetween, said spring means including elongated threaded means extending into said supporting structure and movable inwardly and outwardly relative thereto, a helical spring concentric with said elongated threaded means and in operative engagement at one end thereof with said supporting member for urging said one element toward said other element under the pressure of said spring when said elongated threaded means is screwed inwardly relative to said supporting structure, adjusting means movably carried on said elongated threaded means and coasting with the opposite end of said spring for adjusting the tension thereof, and thrust means rigidly carried on said elongated threaded means for releasing the pressure of said spring from said supporting member when said elongated threaded means is screwed outwardly from said supporting structure whereby to permit disengagement of said elements from the article.

7. A knurling device comprising a base member, a knurling element in the form of a roller journalled in said base member, an anvil support pivotally mounted on said base member, an anvil element carried on said support in substantial alignment with said knurling element whereby said elements are supported in pivotal relation for movement toward and away from each other, means for efifecting relative rolling movement between the knurling element and an article to be knurled, and releasable spring means for yieldingly urging said anvil element toward said knurling element during said rolling movement whereby to clamp the article in knurling position therebetween, said spring means including elongated threaded means extending through said anvil support into said base member and movable inwardly and outwardly relative thereto, a helical spring encircling said elongated threaded means and in operative engagement at one end thereof with said anvil support for urging said anvil element toward said knurling element under the pressure of said spring when said elongated threaded means is screwed inwardly relative to said anvil support, an adjusting nut movably carried on said elongated threaded means and coacting with the opposite end of said spring for adjusting the tension thereof, and thrust means rigidly carried on said elongated threaded means for releasing the pressure of said spring from said anvil support when said elongated threaded means is screwed outwardly relative to said support whereby to permit disengagement of said elements from the article.

8. A knurling device comprising a base member having a swivel mounted therein, a knurling element in the form of a roller journalled in said base member, an anvil support pivotally mounted on said base member, an anvil element carried on said support in substantial alignment with said knurling element whereby said elements are supported in pivotal relation for movement toward and away from each other, means for effecting relative rolling movement between the knurling element and an article to be knurled, and releasable spring means for yieldingly urging said anvil element toward said knurling element during said rolling movement whereby to clamp the article in knurling position there'between, said spring means including elongated threaded means extending through said anvil support into said swivel and movable inwardly and outwardly relative to said support, a helical spring encircling said elongated threaded means and in operative engagement at one end thereof with said support for urging said anvil element toward said knurling element under the ressure of said spring when said elongated threaded means is screwed inwardly relative to said support, an adjusting nut movably carried on said elongated threaded means and coacting with the opposite end of said spring for adjusting the tension thereof, and thrust means rigidly carried on said elongated threaded means for releasing the pressure of said spring from said anvil support when said elongated threaded means is screwed outwardly relative to said support whereby to permit disengagement of said elements from the article, said swivel permitting pivotal movement of said elongated threaded means to accommodate the pivotal movement of said anvil support during said disengagement.

9. A knurling device comprising a base member, a supporting member pivotally mounted on said base member, a knurling element in the form of a roller journalled in one of said members, an anvil element carried on the other of said members in substantial alignment with said knurling element whereby said elements are supported in piovtal relation for movement toward and away from each other, means for eiTecting relative rolling movement between the knurling element and an article to be knurled, and releasable springmeans for yieldingly urging one of said elements toward the other of said elements during said rolling movement whereby to clamp the article in knurling position therebetween, said spring means including an elongated screw threaded into said base member and axially movable inwardly and outwardly relative thereto, a helical spring concentric with said screw and in operative engagement at one end thereof with said supporting member for urging said one element toward said other element under the pres sure of said spring when said screw is moved inwardly relative to said base member, adjusting means movably carried on said screw and coacting with the opposite end of said spring for adjusting the tension thereof, and a thrust collar rigidly carried on said screw for operatively engaging said supporting member and pivoting the latter in the opposite direction when said screw is moved outwardly from said base member whereby to release the pressure of said spring from said supporting member and effect disengagement of said elements from the article.

10. A knurling device comprising a base member, a supporting member pivotally mounted on said base member, a knurling element in the form of a roller journalled in one of said members, an anvil element carried on the other of said members in substantial alignment with said knurling element whereby said elements are supported in pivotal relation for movement toward and away from each other, means for effecting relative rolll5 ing movement between the knunling element and an article to be knurled, and releasable spring means for yieldingly urging one of said elements toward the other of said elements during said roii'ing movement whereby to clamp the article 5 in knurling position therebetween, said spring means including a pair of elongated. coaxial threaded members connected endwise for relative axial movement therebetween and extending through said supporting member into said base member, the inner of said threaded members being secured in said base member and the outer of said threaded members being movable 'in ward'ly and outwardly relative to said supporting member, 'a helical spring concentric with the outer of said threaded members in operative engagement at one 'end thereof with said supporting member for urging said one element toward said other element under the pressure of said spring when said outer threaded member is screwed ingo wardly reiative to said supporting member, ad j'usting means movably carried on said outer threaded member and coacting with the opposite end of said spring for adjusting the tension thereof, and a thrust collar rigidly carried on said outer threaded member for operatively engaging said one end of said spring when said outer threaded member is screwed outwardly relative to said supporting member whereby to effect disengagement of said spring from said supportso ing member and thereby permit release of said elements from the article.

11. A knurling device comprising an elongated base, a knurling roller journaled in said base, a bell crank pivotally supported on said base for rocking movement transversely of said base, an anvil supporting arm extending longitudinally of said base from one leg of said bell crank, an anvil member at the outermost end of said arm in substantial alignment with the knurli-ng roller for clamping an article to be knurled therebetween, driving means connected to said knurling roller for effecting relative rolling movement between said roller and said article, and spring means cooperating with the other leg of said bell crank ior yieldin'gly urging said anvil member toward said knurling roller, said spring means including a screw operatively connected to said base for axial movement relative thereto, a helical spring carried on said screw for actuating said 59 other leg of said bell crank, adjusting means on said screw ior adjusting the tension of said sprin g, means for rotating said screw relative to said base for releasing spring pressure from the bell crank, and means on said screw for actuating said other leg of said bell crank when said screw is move outwardly from said base whereby said anvil member is moved away from said knurling roller for disengaging the same from said article and the spring tension is maintained substantially unchanged.

12. A knurling device comprising an elongated base, a knurling roller Journaled in said base, driving means connected to said hnurling roller for 'eii'ecting relative rolling movement between said roller and an article to be knurleda bell crank pivotally supported on said base for rock ing movement transversely of said base, said bell crank comprising an upright leg and an cut wardly projecting leg having a pin rotatably mounted at its outer end, an anvil 'supportin'g arm extending longitudinally of the base from said upright leg and having an anvil member at its outermost end in substantial alignment with the knurling roller, a swivel mounted in said base, an elongated screw extending transversely through an aperture in said pin and being threaded to said swivel, a helical spring carried on'said screw and adapted to hear at one end against said pin for urging said anvil member toward said lmurling roller for clamping said article therebetween during knurling position of the de vice, an adjusting nut on said screw at the opposite end of said spring -for regulating the tension of the latter, a thrust collar rigidly secured to said screw on the opposite side of said pin, and means for moving said screw outwardly from said swivel while maintaining the sprin tension, said thrust collar being adapted to engage said pin clu ing outward movement of said screw for rocking said bell crank and thereby moving said anvil member away from said knurling roller for disengaging the same from said article.

CERNYW F. JONES;

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1385,212 Shaw Dec. 16, 1930 2,083,775 Carroll June 15, 1937 

